#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <errno.h>
int main()
{
	FILE* x = fopen("test.txt", "w");
	if (x == NULL)
	{
		printf("%s", strerror(errno));
		return 0;
	}
	fseek(x, 4, SEEK_SET);
	fputc('x', x);
	fclose(x);
	return 0;
}
SEEK_CUR
SEEK_END
SEEK_SET